# Amber99sb-disp (ff for disordered and ordered proteins)

**URL:** <https://ask.bioexcel.eu/t/amber99sb-disp-ff-for-disordered-and-ordered-proteins/2245>\
**Category:** General Topics in Molecular Dynamics\
**Created:** [June 23, 2020, 3:28pm UTC](https://ask.bioexcel.eu/t/amber99sb-disp-ff-for-disordered-and-ordered-proteins/2245 "2020-06-23T15:28:29Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![daniele.montepietra](https://avatars.discourse-cdn.com/v4/letter/d/59ef9b/32.png) [@daniele.montepietra](https://ask.bioexcel.eu/u/daniele.montepietra)\
**Post date:** [June 23, 2020, 3:28pm UTC](https://ask.bioexcel.eu/t/amber99sb-disp-ff-for-disordered-and-ordered-proteins/2245/1 "2020-06-23T15:28:29Z")

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Hi there! I’m running simulation of a protein containing extended intrinsically disordered regions.  
I want to use the amber99sb-disp force fiels, that is the state of the art force field for intrinsically disordered proteins, but that also considers ordered regions ( Robustelli P, Piana S, Shaw DE. Developing a molecular dynamics force field for both folded and disordered protein states. _Proc Natl Acad Sci U S A_ . 2018;115(21):E4758-E4766. doi:10.1073/pnas.1800690115 )  
It was developed using Desmond, but they converted it to be GROMACS compatible.  
It simply uses a tip4p model with increased dispersion corrections.  
The problem is that I get these WARNING when I run the equilibration phase with only a box of water (to benchmark it):

WARNING: There are no atom pairs for dispersion correction  
Long Range LJ corr.: 0.0000e+00

Someone knows how to deal with this problem?